Hydrophobic extracted neem oil--a novel insecticide

ABSTRACT

A novel insecticide derived from a neem seed extract comprising neem oil which is substantially free of azadirachtin, said neem oil being prepared by extracting dried, coarsely ground neem seeds with a non-polar, hydrophobic solvent to obtain a neem oil extract, and then removing the solvent to obtain the neem oil. These neem oil insecticides exhibit the ability to repel insects from plant surfaces and kill insect pests at various life stages.

This is a continuation of application Ser. No. 947,867, filed Sep. 21,1992, now abandoned, which is a continuation-in-part application of U.S.Ser. No. 456,762, filed Dec. 26, 1989, abandoned.

FIELD OF THE INVENTION

This invention relates to novel insecticide and fungicide compositionsderived from neem seeds, and more specifically to a novel insecticideand fungicide comprising a hydrophobic-solvent extracted neem oil. Theneem oil extracts of the invention exhibit the ability to repel insectsfrom plant surfaces, prevent fungal growth and kill insect and fungalpests at various life stages.

BACKGROUND OF THE INVENTION

The neem tree, a tropical evergreen, has been used for centuries as asource of pesticides to which insects have not developed a resistance.Various neem seed extracts, particularly the ones containing thehydrophilic, tetranortriterpenoid azadirachtin, are known to influencethe feeding behavior, metamorphosis (insect growth regulating [IGR]effect), fecundity, and fitness of numerous insect species belonging tovarious orders.

It is known that neem oil, containing azadirachtin, may be mechanicallypressed from neem seeds in the cold by using oil presses or may beextracted using alcohols or other solvents using Soxhlet apparatus.Small amounts of neem oil can be obtained by kneading neem seed powderby hand after adding some water (Schmutterer & Helip 1988). Thus theterm `neem oil` has been used to describe a variety of materialscontaining a mixture of both hydrophilic and hydrophobic extractables.The variety of extraction methods and resultant variety in compositionof neem oil has led to great confusion as to the true properties of"neem oil". Khan and Wassilew (1986) tested the effect of their "neemoil" (prepared by aqueous extraction of neem kernels) on 14 commonfungi, including Trichophytonrubrum, T. violaceus, T. concentrichus, T.mentagrophytes, Epidermophyton floccosum, Mierosporum citaneum,Scrophulariopsis brevicaulis, Geotrichum candidum and Fusarium sp andfound that it did not inhibit fungal growth and, in fact, the neem oilitself actually contained several species of growing fungi. Yet ananonymous article (Anon. 1986) reported that "10% Neem oil diluted fromits emulsifiable concentrate formulation" completely inhibited severalspecies of fungi such as Aspergillus niger, Fusarium moniliforme,Macrophomina phaseolina and Drechslera rostrata. However, the specificdetails of this formulation were not provided.

Similarly, there are discrepancies in the literature as to the use ofneem oil to control insects. Schmutterer and Hallpap (1986) showed thataqueous neem seed extracts are significantly superior to neem oil inrepelling leaf mites (Scrobipalpa ergasina), leaf roller (Phycitamelogenu) and leaf hopper (Jacobiella facialna). Mansour et al. (1986)report that the pentane extract of neem seeds was much more effective atcontrolling the spider mite Tetranychus cinnabarinus than were ethanolor methanol extracts, but surprisingly, the pentane extract was lesseffective at controlling the mite, Phytoseiulus persimilis than were theethanol or methanol extracts.

Yamasaki et al showed that the tetranortriterpenoid, salannin, can beisolated from crude plant extracts, obtained from Indian neem seedswhich are known to be high in salannin content, using hexane. Thebiological activity of the salannin extract is reported to be feedingdeterency and growth inhibition when applied to chewing insects such asbeetles and caterpillars.

This invention provides a novel neem oil extract that is substantiallyfree of azadirachtin and yet is effective as both a fungicide and aninsecticide, in particular as a foliar fungicide and insecticide.

It has now been discovered that under the process of this invention, anon-polar, hydrophobic-solvent extracted neem oil, substantially free ofazadirachtin, possesses the ability to repel insects from plantsurfaces, kill insects at various life stages in particular the egg andlarval stages, and control the growth of serious fungal pathogens. Thisdual activity as both an insecticide and a fungicide in the absence ofazadirachtin is novel and unique.

The insecticide and fungicidal activities of the hydrophobicallyextracted neem oil is unique and unexpected in view of the absence ofany known active ingredients.

SUMMARY OF THE INVENTION

It is an object of this invention to provide a novel insecticide thatrepels insect pests from plant surfaces and kills insects at variouslife stages, in particular the egg and larval stages.

It is also an object of this invention to provide a novel fungicide thatcontrols the growth of various fungi.

Another object of this invention is to provide natural insecticide andfungicide formulations derived from neem seed extracts for theprotection of plants from various insect pests and fungi.

In accordance with the present invention, there have been providedcertain novel .insecticide and fungicide formulations derived from neemseed extracts, said formulations comprising non-polarhydrophobic-solvent extracted neem oil fractions, that are substantiallyfree of azadirachtin.

DETAILED DESCRIPTION

As used herein, the term "insecticide" is intended to encompass insectrepellents, larvacides, ovicides and the like. The term "insecticidallyeffective amount" or "fungicidally effective amount" is meant thatdosage of active substance sufficient to exert the desired insecticidalor fungicidal activity.

Some active ingredients of the seeds and leaves of the tropical neemtree, Azadirachtin indica, particularly the tetranortriterpenoidsazadirachtin and salannin, are known for their potent insecticidalactivities. The present invention is directed to various insecticide andfungicide formulations prepared from non-polar hydrophobic solventextracted neem oil which are substantially free of azadirachtin andsalannin, and yet said formulations possess the ability to repel insectpests from plant surfaces, kill insect pests at various life stages, inparticular the egg and larval stage, and control fungal pathogens. Forpurposes of this invention, the term "substantially free ofazadirachtin" is used herein to indicate non-polar hydrophobic solventextracted neem oil having less than 1 weight percent of azadirachtin,preferably less than 0.2 weight percent of azadirachtin, most preferablyless than 0.06 weight percent of azadirachtin.

Neem seeds can be quite variable in size, shape and composition. Seedsfrom around the world can be as small and round as a pea and as largeand long as a bean. Neem seeds consist of two parts, a shell that doesnot contain oil or insecticidal activity and the kernel which containsoil and azadirachtin. However, the composition of seeds collected fromthroughout the world varies considerably as shown in Table A. Inparticular we have found that oil derived from neem trees with highazadirachtin concentration is both insecticidal and fungicidal.

                  TABLE A                                                         ______________________________________                                                  % Kernel             Content                                                                              AZAD                                    Seeds Source                                                                            in Seed    % Volatile                                                                              Oil %  mg/gsk*                                 ______________________________________                                        Senegal (Pout)                                                                          54         7         22     6.6                                     India (Punjab)                                                                          55         5.8       30     1.6                                     Togo      57         7.3       27     4.5                                     (Atkpame)                                                                     Haiti (Arcahie)                                                                         51         12.0      19     2.7                                     Ghana (Bawk)                                                                            57         6.4       14     3.9                                     ______________________________________                                         *gsk = gram seed kernel                                                  

The insecticide and fungicide formulations of this invention areprepared from neem oil which has been extracted from dried, coarselyground neem seeds with a suitable non-polar, hydrophobic solvent. Inaccordance with this invention, dried neem seeds, typically containingabout 5 to 15% water, are coarsely ground to about 5 mesh. The groundneem seeds are then extracted with a non-polar hydrophobic solvent toremove neem oil. It is preferred to use a significant excess of solvent(≧3 to 1 w/w) to obtain good yields. The solvent must be suitablyhydrophobic to prevent excess water from contaminating the product.Water in the extract will cause azadirachtin to be extracted from theseeds and result in hydrolysis of the extract. After extraction,substantially all of the solvent is removed from the extract by lowtemperature evaporation, preferably by vacuum evaporation, to yield theneem oil product.

In the compositions and formulations of the invention, the neem oil maybe used alone or mixed with conventional inert agronomically acceptable(i.e. plant compatible and/or insecticidally inert) orphysiologically-compatible (depending upon the intended use of theinsecticide) adjuvants such as surfactants, stabilizers, antifoam agentsand antidrift agents may also be added. Examples of compositions andformulations according to the invention include aqueous suspensions anddispersions, oily dispersions, pastes, dusting powders, wettablepowders, emulsifiable concentrates, flowables, granules, baits, invertemulsions, aerosol compositions and fumigating candles.

The compositions and formulations are prepared in a known manner to oneskilled in the art, for example by extending the active compounds withconventional dispersible liquid diluent carriers and/or dispersiblesolid carriers optionally with the use of carrier vehicle assistants,e.g., conventional surface-active agents, including emulsifying agentsand/or dispersing agents, whereby, for example, in the case where wateris used as diluent, organic solvents may be added as auxiliary solvents.

Adhesives such as carboxymethylcellulose and natural and syntheticpolymers in the form of powders, granules or latices, such as gumarabic, polyvinyl alcohol, polyvinyl cellulose, and polyvinyl acetate,can be used in the formulations to improve the adherence of thisinsecticide. Furthermore, a lubricant such as calcium stearate ormagnesium stearate may be added to a wettable powder or to a mixture tobe granulated.

The neem oil of the present invention may be employed alone and/or withsuch solid and/or liquid dispersible carrier vehicles and/or with otherknown compatible active agents, especially plant protection agents, suchas other insecticides, arthropodicides, nematicides, fungicides,bactericides, rodenticides, herbicides, fertilizers, growth-regulatingagents, synergists, etc., if desired, or in the form of particulardosage preparations for specific applications made therefrom such assolutions, emulsions, suspensions, powders, pastes, and granules whichare thus ready for use.

In general, insecticidal and fungicidal formulations in accordance withthis invention can be prepared by diluting the neem oil with about 5 to50%, preferably 5 to 20% and most preferably 7 to 15%, by volumeemulsifying surfactant and may optionally contain 0-1% PABA or other UVscreening material. Suitable emulsifying surfactants include sorbitanesters, ethoxylated and propoxylated mono- and diglycerides, acetylatedmono- or diglycerides, lactylated mono- or diglycerides, citric acidesters of mono- or diglycerides, sugar esters, polysorbates,poly-glycerol esters, and the like, and mixtures thereof. The preferredemulsifying surfactants are the polyoxyethylene derivatives of fattyacid partial esters of sorbital anhydrides which are sold under the nameTween 20, Tween 40, Tween 60 and Tween 80. Prior to final application,these insecticidal and fungicidal formulations are typically dilutedwith water.

For foliar application it has been observed that rates of 0.1 to 10%,preferably 0.25 to 3%, neem oil diluted in water are effective forcontrol of insect pests and fungal diseases without unacceptable plantdamage. Neem oil may also be used at various dilutions to controlvarious pest and disease problems on turf, horticultural andagricultural crops as well as stored fruits and vegetables. The neem oilformulations have been shown to be effective at controlling such insectpests as Colorado Potato Beetle, Diamond Backed Moth, Whitefly, Mealybug, Aphids, Hornworm, Lacebug, mites, fleas, ticks, mosquitoes andflies and the like. They are also effective at controlling fungi such asmildews, rusts, dollar spot, brown patch, black spots, botrytis, and thelike. Furthermore, the neem oil can be used to control parasitic pestson mammals such as lice, ticks, scabies, as well as eczema anddermatitus. The neem oil of this invention is particularly useful torepel moths in a confined space, i.e., closets.

Suitable non-polar, hydrophobic solvents for use in extracting the neemoil from the ground neem seeds will include those solvents having highneem oil solubility and substantially no azadirachtin or watersolubility. The preferred non-polar solvents include, but are notlimited to, aliphatic hydrocarbons and halogenated aliphatichydrocarbons such as pentane, hexane, heptane, octane, nonane, decane,isooctane, chloropentane, chlorohexane, and the like, and their isomers;petroleum distillates, petroleum ether, and the like; aromatics andsubstituted aromatics such as benzene, toluene, chlorobenzene,benzaldehyde, xylenes, and the like; and mixtures thereof. Various othernon-polar solvents having the above characteristics are well known tothose skilled in the art, and the choice of a particular solvent is notper se critical to the invention, provided that azadirachtin issubstantially insoluble therein and neem oil has a high degree ofsolubility therein.

Without further elaboration, it is believed that one skilled in the art,using the preceding detailed description, can utilize the presentinvention to its fullest extent. The principles, preferred embodimentsand modes of operation of the present invention have been described inthe foregoing specification. The following examples are provided toillustrate the invention in accordance with the principles of thisinvention, but are not to be construed as limiting the invention in anyway except as indicated in the appended claims. Variations and changesmay be made by those skilled in the art without departing from thespirit of the invention. All parts and percentages are by weight unlessotherwise indicated.

EXAMPLE 1

This example illustrates the effectiveness of the non-polar, hydrophobicsolvent extracted neem oil formulations of this invention on newly laidor near-to-hatch greenhouse whitefly (Trialeurodes vaporariorum) eggs.Eighty (80) kgs of dried defruited neem seeds from Africa were ground ina cutting mill to about 10 mesh. The ground seeds were added to a 300gallon agitated vessel together with 140 gallons (259 kgs) of hexane andagitated for 18 hours. The extracted seeds were then separated from thehexane-neem oil solution by centrifugation. The hexane-neem oil solutionwas transferred to a 500 ml jacketed agitated vessel where the solutionwas heated to 165° F. to remove the excess hexane. The recovered neemoil had a hexane content of <1% and contained about 0.01 weight percentof azadirachtin. The extracted neem oil was formulated into respective1% and 3% solutions in 100 mls of water containing 1 drop of surfactant(Ivory™ Liquid). To test the effectiveness of these formulations, 25potted chrysanthemum plants, cv. Iceberg, had all but 3 fully-expandedleaves removed. The plants were placed in a whitefly colony for 24hours, removed, and sprayed with a water-mist to remove the adultwhiteflies from the plants. The plants were divided into 5 groups of 5and treated as follows:

Group 1) sprayed with water 0 days after exposure (DAE) to whiteflies,

Group 2) sprayed with 1% neem oil formulation 0 days after exposure towhiteflies,

Group 3) sprayed with 3% neem oil formulation 0 days after exposure towhiteflies,

Group 4) sprayed with 1% neem oil formulation 4 days after exposure towhiteflies, and

Group 5) sprayed with 3% neem oil formulation 4 days after exposure towhiteflies.

The greenhouse whitefly eggs usually hatched 5-6 days after oviposition,thus the 4 DAE treatments were applied near the time of egg hatch. Onceall the eggs had hatched on the control plants (those sprayed withwater), the effectiveness of the oil fraction was assessed by countingthe unhatched eggs and dead nymphs per leaf. The results were asfollows:

                  TABLE 1                                                         ______________________________________                                        Effect of Neem Oil When Sprayed on New and 4-Day-                             Old Greenhouse Whitefly Eggs Laid on Chrysanthemums                                                     Dead                                                Treatment   Eggs*         Nymphs*                                                                              % Mortality**                                ______________________________________                                        Water       317    ab     2    c   0                                          1%, 0 DAE   185    b      100  bc  54                                         3%, 0 DAE   153    b      143  b   93                                         1%, 4 DAE   198    ab     180  b   90                                         3%, 4 DAE   360    a      358  a   99                                         ______________________________________                                         *Values are means per 100 cm.sup.2 leaf area. Means within trial followed     by the same letter are not significantly different; DMRT, P = 0.05, N = 1     leaves.                                                                       **Number of dead nymphs divided by the number of eggs.                   

The extracted neem oil at both concentrations and exposure times causedsignificant nymphal mortality. It was observed that most nymphs died asthey were emerging from the egg case. The extracted neem oil was mosteffective on the older eggs applied at a concentration of 3%.

EXAMPLE 2

This example illustrates the effectiveness of extracted neem oil as arepellant to adult Bemisia tabaci whiteflies when sprayed onchrysanthemum foliage. The extracted neem oil was prepared and dilutedinto 1% and 3% formulations according to Example 1. To test theeffectiveness of these formulations, nine 3-week-old pottedchrysanthemum plants cv. Iceberg, having all but 3 fully expanded leavesremoved, were divided into three groups of 3 and treated as follows:

Group 1) sprayed with water,

Group 2) sprayed with 1% neem oil formulation,

Group 3) sprayed with 3% neem oil formulation, and then exposed to acolony of whiteflies for 24 hours. After exposure, the plants werecleaned of adult whiteflies and the number of eggs per leaf wasdetermined. The results were as follows:

                  TABLE 2                                                         ______________________________________                                        Repellency of Neem Oils Against                                               Bemisia tabaci on Chrysanthemums                                                     Treatment     Eggs*                                                    ______________________________________                                               Water         110.0  a                                                        1%            18.0   b                                                        3%            0.0    b                                                 ______________________________________                                         *Values are means calculated per 100 cm.sup.2 leaf area. Means followed b     the same letter are not significantly different; DMRT, P = 0.05, N = 9        leaves.                                                                  

The results show that extracted neem oil is effective at repellingBemisia whiteflies at both concentrations.

EXAMPLE 3

This example illustrates the longevity of repellant action ofhydrophobic solvent extracted neem oil when sprayed on chrysanthemumfoliage cv. Iceberg. Repellency was quantified by counting the number ofgreenhouse whitefly (Trialeurodes vaporariorum) eggs laid on leaves.Neem oil formulations were prepared according to Example 1. Forty eight3-4 week old chrysanthemum plants cv. Iceberg having all but 3 fullyexpanded leaves removed, were divided into three groups of 16 plantseach and treated as follows:

Group 1) sprayed with water,

Group 2) sprayed with 1% neem oil formulation,

Group 3) sprayed with 3% neem oil formulation.

On the same day as spraying (Day 0) 4 plants from each group were placedin a whitefly colony for 24 hours. On days 3, 7 and 14, 4 more plantsfrom each group were exposed to the whitefly colony for 24 hours. Aftereach exposure, the number of eggs per 100 cm² of leaf area on the top 2treated leaves were counted. The results were as follows:

                  TABLE 3                                                         ______________________________________                                        Neem Oils -- Residual Effects                                                        Mean No. Eggs/100 cm.sup.2 Leaf Area*                                  Treatment                                                                              Day 0         Day 3   Day 7   Day 14                                 ______________________________________                                        Water    506    a      844  a    405  a    72   a                             1%       69     b      107  b    14   b    39   a                             3%       18     c      17   b    1    b    5    b                             ______________________________________                                         *Means in same column followed by the same letter are not significantly       different; DMRT, P = 0.05, N = 8 leaves.                                 

The extracted neem oil formulations repelled ovipositing T. vaporariorumfor up to 14 days after spraying. There were no clear differences in thelevel of repellency between the 1% and 3% concentration, or the timebetween treatment and exposure.

EXAMPLE 4 Control of Bean Rust by Extracted Neem Oil

Neem oil was extracted according to the procedure in Example 1. Theextracted neem oil contained 0.01% azadirachtin and was mixed with waterand diluted to 0.25, 0.5, and 1% and sprayed on the fully expandedprimary leaves of beans cv. Pinto 111 until run off. The leaves werethen inoculated with bean rust (Uromyces phaseoli) spores and placed ina dew chamber to allow infection. After approximately 16 hours the beanplants were removed from the dew chamber and placed in a greenhouse.After seven (7) days the number of rust pustules was counted. Theresults, in Table 4, show that the extracted neem oil is an effectivefoliar fungicide at these concentrations.

                  TABLE 4                                                         ______________________________________                                        Treatment    Pustules/100 cm2*                                                                          % Control                                           ______________________________________                                        Control        1174.4  a      0                                               0.25%          220.0   b      81.1                                            0.50%          116.6   b      90.2                                            1.00%          114.2   b      90.2                                            ______________________________________                                         *Treatments with same letter are statistically similar; DMRT, P = 0.05, N     = 6 leaves.                                                              

EXAMPLE 5 Effect of Extracted Neem Oil and Margosan-O® Insecticide onthe Repellency of Whiteflies

Extracted neem oil as prepared in Example 1 was compared to Margosan-O®insecticide containing the insect repellent azadirachtin. In theseexperiments 3 plants each were sprayed with water (control sample), a 2%solution of Margosan-O® insecticide or a 2% solution of neem oil untilrun off. The plants were then placed in a chamber containing a colony ofgreenhouse whiteflies (Trialeurodes) for 2 hours. The plants were thenremoved from the chamber, the adults removed, and the number of eggslaid per cm2 of leaf area counted. The results presented in Table 5 showthat extracted neem oil is a much better repellent than Margosan-O®insecticide or the control.

                  TABLE 5                                                         ______________________________________                                        Treatment                      Repellency                                     Factor          Eggs laid/cm2 Area*                                                                          Factor                                         ______________________________________                                        Control            8.70   a        0                                          Margosan-O ® insecticide                                                                     1.13   b        7.7                                        Extracted Neem Oil 0.058  c        150                                        ______________________________________                                    

EXAMPLE 6 Control of Mildew on Hydrangea

A solution of 2% non-polar, hydrophobic solvent extracted neem oil(0.052 weight percent of azadirachtin) in water was sprayed on 5hydrangea plants growing in greenhouse. The treated plants and an equalnumber of untreated plants were exposed to the natural mildewmicrorganisms found in the greenhouse for 6 weeks. At the end of thisperiod the leaves of the plants were examined for mildew infestation.The untreated plants had an average of 46% of their leaves infestedwhile the treated plants had 1.7% infestation.

EXAMPLE 7

This example illustrates the potent ovicidal activity and repellentfeeding deterrency of hydrophobic solvent extracts of neem seeds. Neemoil containing 0.026 weight percent azadirachtin was extracted accordingto the procedure in Example 1, and diluted with water and surfactantinto 0.22%, 0.66% and 2.0% neem oil formulations. A series of tests wererun on 6 types of insect eggs, both young and old, including: Coloradopotato beetle, tomato hornworm, housefly, Hawthorn lacebug, two-spottedspider mite, and greenhouse whitefly. The eggs were sprayed with water(as a control) and the 3 above neem oil formulations, and the number ofhatching eggs was determined. The results were as follows:

                  TABLE VII                                                       ______________________________________                                        Ovicidal Activity of Neem Oil                                                              Dose  % Egg Mortality                                            Insect         (%)     Young Eggs  Old Eggs                                   ______________________________________                                        Colorado Potato Beetle                                                                       0        8          13                                                        0.22    81           9                                         Tomato Hornworm                                                                              0        8          16                                                        0.22    11          26                                                        0.66    46          42                                                        2       90          77                                         Hawthorn Lacebug                                                                             0       26          33                                                        0.22    30          39                                                        0.66    32          41                                                        2       75          69                                         Two-Spotted Mite                                                                             0       16          12                                                        0.22    54          33                                                        0.66    81          52                                                        2       90          95                                         Greenhouse Whitefly                                                                          0        6          12                                                        0.22     20*         27*                                                      0.66     30*         42*                                                      2        41*         49*                                       ______________________________________                                         *All treated insects died after hatching.                                

As is clear from the above table, the 2% neem oil was effective atcontrolling hornworm, lacebugs, mites and whitefly eggs whether theywere young or old. Young Colorado potato beetle eggs were effectivelykilled by 2% neem oil.

We claim:
 1. A miticide comprising an miticidally effective amount of anon-polar hydrophobic solvent extracted neem oil which has less than 1weight percent of azadirachtin, and which has been treated to remove thenon-polar solvent, wherein the non-polar, hydrophobic solvent has neemoil solubility and substantially no azadirachtin and water solubility.2. The miticide according to claim 1 wherein the neem oil has less than0.2 weight percent of azadiracthin.
 3. The miticide according to claim 1wherein the neem oil is diluted with 5 to 50% by volume of anemulsifying surfactant.
 4. The miticide according to claim 1 wherein theneem oil is diluted with 7 to 15% by volume of an emulsifyingsurfactant.
 5. A mite repellant comprising the miticide of claim 1.